This invention relates to an electric discharge machine, and more particularly to improvements in a wire-cut or band-cut electric discharge machine which is adapted to permit automatic repair of the wire or band electrode should the electrode break during a machining operation.
An electric discharge machine which uses a wire or band electrode as a cutter establishes a voltage differential between the electrode and a workpiece to induce an electrical discharge or spark in the intervening space. The machine moves the workpiece relative to the wire electrode on the basis of data representative of machining instructions, thereby allowing the workpiece to be machined into a desired shape owing to the action of the electrical discharge. There are occasions where the electrode breaks within the workpiece during the machining operation if such machining conditions as the applied voltage and feed speed are improper. In such an event, the operator repairs the broken electrode by pulling it upwardly through a lower guide, passing it again through the hole or slot which has been machined in the workpiece, and then fastening it to a take-up mechanism after passing it through an upper guide. Restoring the wire electrode in this manner so that machining can resume from the former position requires a considerable amount of time and results in diminished machining efficiency. Moreover, since the intervention of the operator is necessary to repair the broken wire electrode, the discharge machining operation will not be able to resume if the wire should break during unattended operation.